A number of solutions have been proposed in the past for laser light projectors or illuminators that will protect the eye-safety of users and viewers. For example, U.S. Pat. No. 6,661,820 by Camilleri et al. (issued Dec. 9, 2003) describes controlling the output power of structured laser light projectors for maintaining eye-safety, including the use of multiple laser diodes. However, their approach provides a separately controlled laser current for each laser diode. Further, the current is controlled by a feedback system incorporating a photodetector and setting the parameters requires software running on an associated processor. Likewise, U.S. Pat. No. 7,925,059 by Hoyos et al. (issued Apr. 12, 2011) describes eye-safety considerations for an iris biometric system incorporating multiple illuminators. The patent teaches a method for determining eye-safety of controlled illuminators, but relies on software for controlling the illuminators. The patent references U.S. Patent Application Publication No. 2006/0274918 by Amantea et al. (published Dec. 7, 2006), that also relies on software running on a processor to compute eye-safe levels.
U.S. Pat. No. 6,922,430 by Biswas et al. (issued Jul. 26, 2005), entitled “Method and apparatus for a multibeam beacon laser assembly for optical communications,” describes an illuminator system with a plurality of laser sources that can be independently adjusted. The eye-safety advantages of multibeam systems are briefly mentioned. There is no mention of circuitry or electronics. U.S. Pat. No. 7,787,767 by Wang, X. (issued Aug. 31, 2010), entitled “Eye safety in electro-optical transceivers,” and patents referenced in the disclosure therein describe signal loss detection circuitry to maintain eye-safety of parallel laser communication systems. These systems rely on monitoring of the output power or received power of one or more of the laser sources.
Additional apparently less relevant patents include U.S. Pat. No. 7,796,081 by Breed (issued Sep. 14, 2010), entitled “Combined imaging and distance monitoring for vehicular applications;” U.S. Pat. No. 7,742,640 by Carlson et al. (issued Jun. 22, 2010), entitled “Reduction of background clutter in structured lighting systems;” U.S. Pat. No. 7,568,802 by Phinney et al. (issued Aug. 4, 2009), entitled “Eye-safe near infra-red imaging illumination method and system;” U.S. Pat. No. 7,232,240 by Kosnik et al. (issued Jun. 19, 2007), entitled “Extended source laser illuminator;” U.S. Pat. No. 6,974,373 by Kriesel (issued Dec. 13, 2005), entitled “Apparatus and methods for the volumetric and dimensional measurement of livestock;” U.S. Pat. No. 6,007,218 by German et al. (issued Dec. 28, 1999), entitled “Self-contained laser illuminator module;” U.S. Pat. No. 5,383,200 by Barrett et al. (issued Jan. 17, 1995), entitled “Eye safe laser imaging system;” U.S. Pat. No. 5,745,515 by Marta and Morgan, (issued Apr. 28, 1980), entitled “Self-limiting intrinsically eye-safe laser utilizing an increasing absorption layer;” U.S. Pat. No. 7,834,302 by Ripingill et al. (issued Nov. 16, 2010), entitled “Eye safety protection from high power laser light;” U.S. Pat. No. 7,911,412 by Benner, Jr. et al. (issued Mar. 22, 2011), entitled “Audience scanning light projector and associated methods;” and U.S. Pat. No. 7,087,886 by Almi et al, (issued Aug. 8, 2006), entitled “Method and a system for multi-pixel ranging of a scene.”